Admin app improvements

[James-Mart]

Tasks

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1. Add missing configurations, mainly for key management and TLS certificate management
2. When creating a block producer name, validate specified name is valid.
3. Actually create the specified block producer account (And create a key for it using auth-sig)
4. Rename BlockProducer name to NodeAccountName on the "Join network" flow.
5. Connect to URL - Send request to check it's online and responding before moving to next page.